The invention relates to the field of door closers, and more particularly concerns varying the force applied to a door by a closer depending on the door operating position.
Door closers are used to automatically close doors, saving people who pass through the doorway the effort of closing the door and helping to ensure that doors are not inadvertently left open. In general, a door closer may be attached to the top of a door, and a pivotable arm extends from the door closer to a door frame or wall. When the door is opened, the door closer automatically generates a mechanical force that actuates the arm, causing the arm to close the door without any manual application of force.
Many conventional door closers are designed to apply varying forces to a door as a function of the door angle, meaning the angle at which the door is open relative to the door frame. A door and door closer may be considered to experience an opening cycle and a closing cycle. With respect to the opening cycle, the door starts in the fully closed or home position, typically where the door is at the jamb. When the door is opened, the door closer generates little force until the door reaches a certain predetermined door angle, which may be designated as the beginning of the backcheck region. As the door enters the backcheck region, the door closer applies force to the door. This force slows the progress of the door, increasing the force required to open the door further, and may help to prevent the door from hitting a wall or otherwise opening past a desired stop point. Increase in force applied by a door closer at other points between the home position and the beginning of the backcheck region may be included as a feature of a particular door closer. Therefore, as the door angle increases or, in other words, as the door is opened wider, it becomes more difficult to continue pushing the door open, usually for protection of an adjacent wall.
When the door is released by the user, for example, from the fully opened position, the force generated by the door closer begins the closing cycle. The door may pass through the backcheck region and to the beginning of a latch region, proximate to the home position, with a substantially constant force applied by the door closer. As the door reaches the beginning of the latch region, very little or no force is applied to the door. If calibrated correctly, the latch region allows the door to close without slamming the door or damaging the door frame, and with relatively low risk of injury to a person's body part struck by the door. Reduction in the force applied by a door closer at other points between the fully open position and the latch region may be included as a feature of a particular door closer.
Many conventional door closers are mechanically actuated and have a piston and a plurality of springs and valved ports. The piston moves through a reservoir filled with a hydraulic fluid, such as oil. The piston is coupled to the door closer's arm such that, as the door is opened, the piston is moved in one direction and, as the door is closed, the piston is moved in the opposite direction. As the piston moves, it displaces hydraulic fluid, which may be forced through various valved ports. By allowing, limiting, or preventing flow of hydraulic fluid, the valved ports control the varying amounts of force applied to the door as a function of door angle. The piston may either cover or expose individual ports to make flow of hydraulic fluid through the ports possible depending position of the piston, as determined by the door angle. The force exerted by the door closer depends on the open or closed status of the ports.
The door's opening and closing profile can be controlled by adjusting the valves, which may often be done by turning a screw to alter the flow characteristics through the valve and thereby control the force applied by the closer. However, this adjustment may be problematic in that the valves interact and changing the setting of one valve generally affects the flow rates of the other valves. Many conventional door closers implement undesirable closing characteristics because installers may be unwilling or unable to manually adjust the valve settings in a desired manner, or installers may be unaware that the valve settings can be changed in order to effectuate a desired closing profile.
Accordingly, there exists a need for a door closer that automatically adjusts after initial calibration, resulting in a door motion that has desirable opening and closing cycles and is relatively easy to install.